In rail vehicle traffic, increasing use is being made of diagnostic and monitoring systems with which state changes of components and assemblies of the rail vehicle are sensed to detect defects in these components and assemblies. In particular, in the case of a wheel set of a rail vehicle, it is of particular interest for operational safety to detect damage and fractures.
As disclosed in EP 1 274 979 B1,the oscillation behavior of at least one vehicle component is monitored by capturing at least one oscillation signal, is subjected to a Fourier transformation and is compared with at least one reference value, wherein the frequency peak which is assigned to a natural oscillation component of the vehicle component is monitored with respect to at least one characteristic value (frequency characteristic value, damping characteristic value, amplitude characteristic value). Thus, the vehicle component is subjected to a modal analysis and modal parameters, e.g., natural frequency and damping being monitored to detect damage in the case of onboard diagnostics. However, the known method evaluates time profiles of the measurement signals in an undifferentiated fashion. In particular, in the method signals acquired under completely different peripheral conditions such as, for example, different static friction conditions or sliding friction conditions are evaluated jointly.
Accordingly, the characteristic values from the Fourier transformation, such as, for example, the values for the natural frequencies and their amplitude maximum values, are subject to relatively large radiation, which makes unambiguous and reliable evaluation of the frequency responses difficult. In particular, the excitation spectrum during operation is so different that at any individual time it is unclear which component on the measured signal the natural oscillations of the respective vehicle component have.
Although the known method provides that the frequency responses which have arisen from the measurements are compared with route-dependent reference frequency responses (new section of line, old section of line, extended section of line), this procedure entails some disadvantages. This is because, on the one hand, for all the sections of lines which can be traveled on during correct operation of the rail vehicle have to be taken into account. On the other hand, the properties of the route must then not be changed by external influences or the reference data have to be kept constantly up to date. However, this requires an inappropriately large amount of expenditure, for which reason the preconditions for application of the known method certainly cannot be complied with in practice.
The known method for monitoring the diagnostics and the state of rail vehicle components is consequently based on continual and continuous measurement and evaluation of measurement variables. However, in this context the peripheral conditions for the measurement variables change constantly. Analysis of the frequency responses acquired from the time signals is very costly because the influence of the peripheral conditions has to be evaluated using route-dependent reference signals.